JP6782546B2 - Plasma chemical vapor deposition equipment and methods - Google Patents

Description

The present invention relates to a plasma chemical vapor deposition (PE-CVD) apparatus and a method for performing plasma chemical vapor deposition.

Plasma chemical vapor deposition is a well-known technique for depositing various materials. It is well known that plasma chemical vapor deposition is performed in the production of semiconductor devices. In common with other semiconductor processing methods, a very important factor in the realization of commercially useful processes is the processing power of the system. The main problem that reduces processing power is in the cleaning process. A cleaning process is required to remove the deposited material from the internal surface of the plasma chemical vapor deposition process chamber. Shortening the time required to perform a cleaning process or between cleaning processes results in higher processing power and lower cost of ownership (COO). Modern cleaning processes have a uniform cleaning rate over the entire surface of the chamber. However, at least some plasma chemical vapor deposition processes result in deposition on the inner surface of the chamber with an uneven distribution of deposition thickness. Silicon nitride deposition, especially at low deposition temperatures, is an example of a plasma chemical vapor deposition process that produces a very uneven thickness distribution of the deposited material.

Plasma chemical vapor deposition is commonly used to process silicon wafers. A typical plasma chemical vapor deposition single wafer chamber system design method is to limit the conduction of gas into the system. This is done with the intention of making the net pumping flow of the system across the wafer radial. The intent is to provide uniform deposition across the wafer. Most commercially available single-wafer plasma chemical vapor deposition systems adjust the ground plane of the system, affect the shape of the plasma, and use ceramic spacers to achieve this radial conduction of the gas. FIG. 1 shows an example of a prior art plasma chemical vapor deposition chamber, all represented by the number 10, including a chamber 12 having a platen 14 arranged therein. A "shower head" 16 at the top of the chamber 12 is used to introduce gas into the chamber 12. As is well known in the art, plasma is formed using a plasma generator (not shown). The system 10 further includes a lower ceramic spacer 18 and an upper ceramic spacer 20. The upper ceramic spacer 20 and the platen 14 define a relatively small first gap 22. The upper ceramic 20 and the lower ceramic 18 define a relatively small second gap 24 leading to the circumferential pumping chamber 26. The circumferential pumping chamber is in gas conduction communication with the pumping port. The pumping port is not shown in FIG. 1, but FIG. 2 clearly shows the pumping port 28 and the wafer take-in slot 29. FIG. 2 will be described in more detail below. The pumping port is connected to an exhaust line containing a suitable pump for exhausting gas from the chamber to maintain the desired pressure inside the chamber. Therefore, the gas is exhausted from the chamber through a flow path that includes a first pumping gap 22, a second pumping gap 24, and a circumferential pumping channel 26. The first and second pumping gaps 22 and 24 are relatively small and reduce the gas conductivity of the system to create a radial flow.

The present invention addresses the above problems in at least some of its embodiments. In particular, the present invention reduces the cleaning time associated with a plasma chemical vapor deposition process in at least some of its embodiments. This in itself can result in improved processing power and lower cost of ownership COO.

According to the first aspect of the present invention, in the plasma chemical vapor deposition apparatus,
With a chamber containing a circumferential pumping channel,
The board support placed inside the chamber and
One or more gas inlets for introducing gas into the chamber,
A plasma generator for generating plasma in the chamber,
With the upper and lower elements placed in the chamber,
Is a device that includes
The top element is spaced apart from the substrate support to confine the plasma and define the first circumferential pumping gap, and the top element acts as a radial inward wall of the circumferential pumping channel. ,
The upper and lower elements are spaced radially apart to define a second circumferential pumping gap that acts as an inlet to the circumferential pumping channel, with the second circumferential pumping gap being the first. Provided is a plasma chemical vapor deposition apparatus that is wider than the circumferential pumping gap.

The lower elements are spaced radially apart from the substrate support and below the circumferential pumping channel, with an auxiliary circumferential pumping channel that overlaps this circumferential pumping channel in the radial direction. To determine. The first circumferential pumping gap may act as an inlet to the auxiliary circumferential pumping channel. The circumferential pumping gap may act as an outlet for the auxiliary circumferential pumping channel.

The lower element may include a base portion and a wall rising from the base portion. The cross section of the lower element may be generally L-shaped.

The lower element may be a liner that contacts a portion of the inner wall of the chamber. The inner wall of the chamber may include one step on which the liner is placed.

The top element may include a hanging wall within the chamber. The wall of the upper element may include an upper part and a lower part. The upper part may be thicker than the lower part.

The wall of the lower element may have a radial inward facing surface. The wall of the top element may have a radial outward facing surface. The radial inward surface of the lower element wall and the radial outward surface of the upper element wall may be spaced radially apart to define a second circumferential pumping gap.

The wall of the top element may act as a radial inward wall of the circumferential pumping channel.

The upper and lower elements may each be formed from a dielectric material. The upper and lower elements may each be formed from a ceramic material.

The upper and lower elements may be annular. Typically, the upper and lower elements are each provided as an integral structure. However, in principle, it is possible to provide one or both of the upper and lower elements in two or more structures. Although each of the upper and lower elements is preferably placed in the chamber as a single structure, one or both of the upper and lower elements are placed in the chamber as a structure arranged at multiple separate intervals. In principle, it is possible to have a multiple structure.

The substrate support may have an upper surface that defines the level when the substrate support is in its position of use. At least a portion of the circumferential pumping channel may be located above the level.

The second circumferential pumping gap may have at least twice the width of the second circumferential pumping gap.

The gas inlet may be provided in any suitable form, such as a shower head. Those skilled in the art will easily come up with many other configurations.

The plasma generator may be of any suitable type, such as those well known to those skilled in the art. An example of a suitable device is a capacitively coupled plasma generator.

According to the second aspect of the present invention, in the plasma chemical vapor deposition method for treating a substrate,
The step of providing the apparatus according to the first aspect of the present invention, and
Steps to place the board on the board support,
In the step of processing the substrate by performing plasma chemical vapor deposition, the gas is introduced into the chamber through one or more gas inlets and the first and second circumferential pumping gaps and circumferences. With steps, which are removed from the chamber through a flow path containing a directional pumping channel,
Methods are provided that include.

The gas is more than 3000 sccm (converted to 5.07 P m ³ / s when 1 standard cc / min is 1.69 × 10 ^-3 P m ³ / s), preferably more than 5000 sccm (8.45 P m ³ / s), most. Preferably, it may be introduced into the chamber at a flow rate greater than 7000 sccm (1.183 × 10 Pa m ³ / s).

Plasma chemical vapor deposition may be performed to deposit silicon nitride on the substrate.

Alternatively, plasma chemical vapor deposition may be performed to deposit silicon dioxide, silicon nitride or amorphous silicon onto the substrate.

It has been pointed out that the relatively high gas conductivity provided by the present invention may reduce the pressure difference between the chamber and the circumferential pumping channel. During the plasma chemical vapor deposition process, the pressure in the circumferential pumping channel may be within 5%, preferably within 4% of the pressure in the chamber.

The substrate may be a semiconductor substrate. The substrate may be a silicon substrate. Typically, the silicon substrate is a silicon wafer.

Although the present invention has been described above, the present invention extends to any inventive combination of features described above or within the scope of the description, drawings or claims below. For example, any feature described in connection with the first aspect of the invention is considered to be similarly disclosed in connection with the second aspect of the invention, and vice versa.

Embodiments of the apparatus and method according to the present invention will be described here with reference to the accompanying drawings.

It is sectional drawing of the plasma chemical vapor deposition apparatus of the prior art. It is a figure which shows the vapor deposition of silicon nitride in the apparatus of FIG. It is sectional drawing of the plasma chemical vapor deposition apparatus of this invention. It is a figure which shows the vapor deposition of silicon nitride in the apparatus of FIG. It is a graph which shows the relationship between the number of processed wafers, the vapor deposition thickness and the thickness non-uniformity.

FIG. 3 shows a plasma chemical vapor deposition apparatus represented by 30 as a whole, including a chamber 32 having a substrate support 34 arranged inside. The substrate support 34 may be a platen on which a semiconductor wafer is placed. Typically, the platen can be moved between a descending position for accommodating the wafer and an ascending position for processing the wafer by plasma chemical vapor deposition. FIG. 3 shows the platen 34 in the raised position of use. The device 30 further includes a shower head 36 located at the top of the chamber 32. The shower head 36 includes a plurality of gas inlets capable of introducing the desired gas or gas mixture from a gas supply system (not shown) into the chamber 32. Typically, a gas mixture containing one or more process gases in combination with one or more carrier gases is supplied to the chamber 32. Plasma is created in the main chamber 32 using a plasma generator (not shown). In this way, the material is deposited on the semiconductor wafer by the desired process. Plasma chemical vapor deposition processes and associated plasma generators are well known to those of skill in the art. In one embodiment, the device 30 shown in FIG. 3 can be implemented using a capacitively coupled plasma generator. The device 30 further includes an upper element 38 and a lower element 40. The upper and lower elements 38, 40, respectively, are in the form of ceramic spacers.

The chamber 32 includes first and second stage divisions 32 (a), 32 (b). The first stage division 32 (a) accommodates the lower element 40, which is an annular ring structure having an L-shaped cross section. The second stage division 32 (a) defines the main circumferential pumping channel in combination with the upper element 38.

Ceramic top and bottom elements 38, 40 are used for one or more known purposes, such as changing the ground plane of the device, affecting the shape of the plasma, and protecting the device from the plasma. It is possible to do. Specifically, the upper element 38 is of an annular shape and is arranged so as to surround the uppermost portion of the wafer and substrate support 34. The upper element acts to trap the plasma. The lower element 40 acts to protect the walls of the chamber 32 from plasma. Further, the upper and lower elements 38, 40 define a part of the flow path through which the gas flows as the gas is discharged from the chamber 32. The upper element 38 is disposed away from the substrate support 34 to define a first pumping gap. The gas flowing through the first pumping gap then enters one region 44, which is the auxiliary pumping channel. The auxiliary pumping channel is defined by a lower element 40 and a lateral region of the wafer support 34. The uppermost portion of the lower element 38 and the lowest portion of the upper element 40 define a second pumping channel leading to the main circumferential pumping channel 42. The main circumferential pumping chamber 42 is in a gas conductive communication state with the pumping port 46. The pumping port 46 is shown in FIG. 4, which also shows the wafer capture port 48. The pumping port 46 is connected to a vacuum line (not shown) containing a suitable pump. The vacuum line may be essentially of conventional construction.

Experiments were performed using the prior art device of FIG. 1 and the device of the present invention shown in FIG. Silicon nitride is deposited in both chambers. FIG. 2 shows that silicon nitride is deposited in the region 27 represented by the symbol X when the prior art device is used. FIG. 4 shows that silicon nitride was deposited at the location 50 represented by the symbol X when the apparatus of the present invention was used. It can be seen that the prior art device deposits silicon nitride very asymmetrically. In contrast, in the device of FIG. 3, the silicon nitride deposition spreads much more evenly throughout the chamber. This is a result of the reduction in the thickness of the silicon nitride deposition on the chamber of the present invention. In comparison, the prior art device produces regions where the deposited silicon nitride is relatively thick. The consequence of thicker deposition obtained with prior art devices is that it takes longer cleaning times to remove the deposited material. Experiments were performed to run a low temperature "via reveal" application to generate a SiN / SiN / SiO stack. It has been found that the apparatus of the present invention reduces the cleaning time from 720 seconds to 130 seconds as compared with the apparatus of the prior art. This results in a substantial improvement in processing power. Similarly, it is pointed out that as a further consequence of the asymmetric deposition pattern shown in FIG. 2, areas with relatively thin deposition layers will be over-cleaned.

Experiments were also carried out to investigate the effect of the present invention on process parameters and film properties for plasma chemical vapor deposition of silicon nitride and silicon oxide using a range of process recipes. The experiment was carried out using a certain number of silicon wafer substrates having a diameter of 300 mm. Table 1 shows important dielectric film properties. It can be seen that the properties of the film obtained using the present invention are far superior to those of the equivalent film obtained using the prior art device. In fact, the measurement properties obtained using the prior art device and the device of the present invention are consistent within the relevant error band for measurement. Similarly, the profiles of the endpoint signal (optical measurement of excited free radical fluorine species in the plasma) and the DC bias signal are very similar using the same NF ₃ cleaning recipe on both types of equipment. I understand. Furthermore, it has been found that the apparatus of the present invention has no effect on the electrical and optical properties of C ₃ F ₈ / O ₂ cleaning.

Table 2 shows the measured pressures in the main chamber and the circumferential pumping chamber of the prior art device of Table 1 and the device of the present invention of Table 3. It can be seen that the prior art device produces a significant pressure difference between the main chamber and the circumferential pumping chamber. This can be easily explained theoretically in terms of the limited pumping gaps 22 and 24 leading to the circumferential pumping channel 26. As described above, this is an arbitrary design feature intended to reduce gas conduction in order to achieve radial flow across the wafer. In contrast, the present invention provides a much reduced pressure difference between the chamber and the circumferential pumping channel. At present, it has not been confirmed whether the flow across the wafer is radial. It is not desired to be limited by any particular theory or speculation, but it is theoretically in view of the larger second pumping gap defined by the spaced upper and lower elements 38, 40. It is believed that it can be explained. It is also possible that the volume and / or flow path of the auxiliary circumferential pumping chamber 44 plays a role. It was pointed out that the absolute pressures in the chambers of both the prior art device and the device of the invention were the same during the plasma chemical vapor deposition process, even if the gas conductivity was higher in the case of the present invention. Will be done. This was achieved by controlling the throttle valve on the exhaust line.

FIG. 5 shows the interwafer film thickness for a typical via exposed SiN / SiO ₂ stack obtained using the apparatus of FIG. Cleaning was performed during successive wafer processing. In FIG. 5, the diamond symbol 52 relates to the SiO ₂ film, the square symbol 54 relates to the silicon nitride vapor-deposited film, and the triangle symbol 56 relates to the thickness of the entire stack. FIG. 5 also shows the non-uniformity of the entire stack. The X symbol 58 means stack non-uniformity data. It was found that the apparatus of the present invention exhibits excellent film properties.

The present invention is believed to provide extremely good results when used in combination with a plasma chemical vapor deposition process with a high gas flow rate. However, the present invention is not limited to high flow processes. The beneficial effects provided by the present invention are not believed to be limited to the explicit process recipes used. Conversely, the present invention is believed to be available for a wide range of vapor deposition recipes to provide a wide range of vapor deposition materials such as silicon oxide, silicon oxynitride and amorphous silicon.

Claims (17)

In plasma chemical vapor deposition equipment
And blood Yanba,
The substrate support placed in the chamber and
One or more gas inlets for introducing gas into the chamber,
A plasma generator for generating plasma in the chamber,
With the upper and lower elements placed in the chamber,
Only including,
The radial inner surface of the top element and the side surface of the substrate support are spaced apart by a first distance in the radial direction of the chamber, which defines the first circumferential pumping gap.
The top element has a radial outward facing surface that separates the radial inside of the main circumferential pumping channel.
The lower elements face the sides of the substrate support in the radial direction of the chamber and are spaced apart from the sides, thereby separating the auxiliary circumferential pumping channels of the chamber, which auxiliary circumferential pumping channels are the main circle. Arranged below the circumferential pumping channel and overlapping in the radial direction of the chamber, the first circumferential pumping gap constitutes the inlet to the auxiliary circumferential pumping channel.
The bottom of the top element and the top of the bottom element are offset by a second distance in the radial direction to form both the entrance to the main circumferential pumping channel and the exit of the auxiliary circumferential pumping channel. Determine the circumferential pumping gap
The second distance is greater than the first distance,
Place the board on the board support and
Gas is introduced from one or more gas inlets into the process area of the chamber located radially inside the main circumferential pumping channel.
Exciting a gas to form a plasma,
Using plasma to deposit material on the substrate,
The gas in the process area of the chamber is removed from the device through the first circumferential pumping gap, the auxiliary circumferential pumping channel, the second circumferential pumping gap, and the main circumferential pumping channel.
Plasma chemical vapor deposition equipment. The plasma chemical vapor deposition apparatus according to claim 1, wherein the lower element includes a base portion and a wall rising from the base portion. The plasma chemical vapor deposition apparatus according to claim 2 , wherein the lower element has a generally L-shaped cross section. The plasma chemical vapor deposition apparatus according to any one of claims 1 to 3 , wherein the lower element is a liner that contacts a part of the inner wall of the chamber. The plasma chemical vapor deposition apparatus according to any one of claims 1 to 4 , wherein the upper element includes a wall hanging in a chamber. The plasma chemical vapor deposition apparatus according to claim 5 , wherein the wall of the upper element includes an upper portion and a lower portion, and the upper portion is thicker than the lower portion. The plasma chemical vapor deposition apparatus according to any one of claims 1 to 6 , wherein the upper element and the lower element are each formed of a dielectric material. The plasma chemical vapor deposition apparatus according to claim 7 , wherein the upper element and the lower element are each formed of a ceramic material. The plasma chemical vapor deposition apparatus according to any one of claims 1 to 8 , wherein the upper element and the lower element are annular. The substrate support is characterized by having an upper surface that determines the level when the substrate support is in its position of use, with at least a portion of the circumferential pumping channel located above the level. The plasma chemical vapor deposition apparatus according to any one of claims 1 to 9 . The plasma chemical vapor deposition according to any one of claims 1 to 10 , wherein the second circumferential pumping gap has a width at least twice the width of the first circumferential pumping gap. Phase vapor deposition equipment. In a method of performing plasma chemical vapor deposition to process a substrate,
The step of providing the apparatus according to claim 1 and
The step of placing the board on at least one board support,
In the step of processing the substrate by performing plasma chemical vapor deposition, the gas is introduced into the chamber through one or more gas inlets and the first and second circumferential pumping gaps and circumferences. With steps, which are removed from the chamber through a flow path containing a directional pumping channel,
A method characterized by including. The gas is introduced into the chamber at a flow rate of more than 3000 sccm (5.07 P m3 / s), preferably more than 5000 sccm (8.45 P m3 / s), most preferably more than 7000 sccm (1.183 x 10 P m3 / s). The method according to claim 1 and 2 . Plasma enhanced chemical vapor deposition to deposit silicon nitride on the substrate is carried out, method according to claim 1 2 or 1 3, characterized in that. The method according to claim 1 2 or 1 3 silicon dioxide on the substrate, carrying out a plasma chemical vapor deposition to deposit silicon oxynitride, or amorphous silicon, characterized in that. Any one of claims 1 2 to 15 characterized in that, during the plasma chemical vapor deposition process, the pressure in the circumferential pumping channel is within 5%, preferably within 4% of the pressure in the chamber. The method described in the section. The method according to any one of claims 12 to 16 , wherein the substrate is a semiconductor substrate such as a silicon substrate.

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